/*******************************************************************************
 * Copyright (c) 2003, 2005 IBM Corporation and others.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *     IBM Corporation - initial API and implementation
 *******************************************************************************/
package com.architexa.org.eclipse.draw2d.graph;

import java.util.Stack;

/**
 * This class takes a DirectedGraph with an optimal rank assignment and a spanning tree,
 * and populates the ranks of the DirectedGraph. Virtual nodes are inserted for edges that
 * span 1 or more ranks.
 * <P>
 * Ranks are populated using a pre-order depth-first traversal of the spanning tree. For
 * each node, all edges requiring virtual nodes are added to the ranks.
 * @author Randy Hudson
 * @since 2.1.2
 */
class PopulateRanks extends GraphVisitor {

private Stack changes = new Stack();

/**
 * @see GraphVisitor#visit(DirectedGraph)
 */
public void visit(DirectedGraph g) {
	if (g.forestRoot != null) {
		for (int i = g.forestRoot.outgoing.size() - 1; i >= 0; i--)
			g.removeEdge(g.forestRoot.outgoing.getEdge(i));
		g.removeNode(g.forestRoot);
	}
	g.ranks = new RankList();
	for (int i = 0; i < g.nodes.size(); i++) {
		Node node = g.nodes.getNode(i);
		g.ranks.getRank(node.rank).add(node);
	}
	for (int i = 0; i < g.nodes.size(); i++) {
		Node node = g.nodes.getNode(i);
		for (int j = 0; j < node.outgoing.size();) {
			Edge e = node.outgoing.getEdge(j);
			if (e.getLength() > 1)
				changes.push(new VirtualNodeCreation(e, g));
			else
				j++;
		}
	}
}

/**
 * @see GraphVisitor#revisit(DirectedGraph)
 */
public void revisit(DirectedGraph g) {
	for (int r = 0; r < g.ranks.size(); r++) {
		Rank rank = g.ranks.getRank(r);
		Node prev = null, cur;
		for (int n = 0; n < rank.size(); n++) {
			cur = rank.getNode(n);
			if (cur instanceof VirtualNode)
				((VirtualNode)cur).left = prev;
			if (prev instanceof VirtualNode)
				((VirtualNode)prev).right = cur;
			prev = cur;
		}
	}
	for (int i = 0; i < changes.size(); i++) {
		RevertableChange change = (RevertableChange)changes.get(i);
		change.revert();
	}
}

}
